This invention relates to the display of video images in the context of electronic video amusement games.
The growing sophistication of video games increasingly requires the display of large numbers of moving objects in a video display. Also, now that color monitors are commonly used, game displays require complex background patterns over which the moving objects move during game play.
Modern video games are frequently designed for microcomputer control. Currently available microcomputers have limited computational power which may readily be overwhelmed by the simultaneous demands of game calculations and display control. Such demands have in the past been met with the use of high speed general purpose computers. The high cost of such computers, however, makes their use impractical in commercially viable video games.
Recent developments in the video game art have been directed to the design of hardware that tends to relieve the game microcomputer from its display control responsibilities. The game microcomputer is then available for game associated computations to the extent that it can delegate the supervision and control of the game display to the display hardware. On the other hand, the display hardware "steals time" from the microcomputer to the extent that the hardware must communicate with the microcomputer and to the extent that the hardware requires microcomputer supervision.
One example of a proposed use of dedicated display hardware is provided by Mayer, et al., U.S. Pat. No. 4,112,422. In Mayer the microcomputer specifies to a separate display circuit the objects that are to be displayed and the display positions of the objects. The display circuit then generates a signal suitable for use by a home TV receiver utilizing counters which are activated when the display positions of the various objects are reached. The design requires one counter for each object to be displayed.
It is evident that the circuitry taught by Mayer, et al., necessarily increases in size, complexity, and expense as the number of objects displayed increases. The Mayer circuitry also requires that the microcomputer operate "in step" with the display circuitry. The display circuitry is not, therefore, substantially "transparent" to the microcomputer operations. The freedom of the microcomputer to perform game computations is also thereby severely limited.
Some of the disadvantages of Mayer, et al., might be obviated by the system of Chung, U.S. Pat. No. 4,177,462. Chung's display circuit utilizes display controllers which act upon data supplied by the microcomputer. Each controller is indicated as having the capability of controlling up to 16 objects and putting a substantially single color background between each pair of objects. The objects are displayed on the basis of data supplied by the microcomputer which must, in turn, interrogate the display circuitry to obtain some of the game computational logic from a replaceable cartridge ROM in the display circuitry.
Chung's display circuit, at best, gives the microcomputer only limited relief from duties that steal time that would otherwise be available for game-associated calculations. The microcomputer is required to be inactivated whenever communications occur between the microcomputer and the display circuitry. A further disadvantage of the Chung design is that it requires the use of content addressable memories which are special purpose devices and tend to be costly. It would be much more desirable for commercial reasons to build circuits using readily available low cost devices in the design of circuitry for arcade games.